Like its more famous cousin, Tornado Alley, Pothole Alley is more than a state of mind, explained Bill Franklin, Toledo public service director. It has no definitive boundaries, but is a collection of cities caught in the middle, climate-wise, he said.

Roads are actually less vulnerable to cracking in the far north, Mr. Franklin said.

In Michigan’s Upper Peninsula, northern Minnesota, or North Dakota, for example, the cold is consistent enough to keep them frozen for extended periods, he said.

To the far south, they aren’t salted much because there isn’t as much need.

But in Pothole Alley, roads are constantly salted. They can’t be left to freeze over because of how often temperatures toggle above and below freezing — a pattern that places the most stress on asphalt, Mr. Franklin said.

“We’re in probably the worst place you can be for potholes,” he said.

Both Mr. Welch and Mr. Franklin said they have no reason to believe the city’s highly unusual number of potholes this year — especially deep ones — has much to do with Toledo’s historical connection to the Great Black Swamp, a flood-prone swath of land across northwest Ohio where mosquitoes made Civil War-era soldiers so miserable that they tried their best to avoid it.

There’s an old saying: Once a swamp, always a swamp. It refers to how nature tries, at times, to revert to its former self.

But drainage, they said, is not the problem. Toledo’s roads drain well.

The problem, according to Mr. Franklin and Mr. Welch, is how Toledo’s climate makes it prone to rapid freeze-thaws, a yo-yo effect capable of serving up a whuppin’ on local infrastructure that includes roads, bridges, sidewalks, water mains, sewer lines, and power lines.

The situation has given city officials and others reason to question the traditional practices of blanketing roads with heavy road salt or chemicals when the temperatures get too cold for salt to be effective.

The problem is that there are few alternatives with public safety tantamount to everything else.

Sand is a possible salt substitute, but it clogs sewers, which could lead to flooded basements. And some claim it’s rougher on auto bodies than salt.

“I hate to say it, but we’re more reacting to things now,” Mr. Welch said. “All we’re trying to do is get through to the warmer weather.”

Season starts early

The city has repaired more than 20,000 potholes so far this season and is on pace to go well beyond the average 60,000 potholes it patches a year.

It typically spends $188,000 a year on pothole repairs. This year, it expects to spend at least $90,000 more, or $278,000.

But those numbers don’t tell the whole story.

For one thing, as bad as potholes are now, many people don’t realize we’re barely into pothole season.

Road breakups that usually start in mid-February began at least a month earlier this winter.

Many more potholes are being formed now. They are expected to continue forming through mid-April.

“The thing is, we haven’t see the worst of the potholes yet,” Mr. Franklin said.

The city has crews working weekends whenever possible, resulting in time and a half on Saturdays and double time on Sundays for city pothole patching crews.

There are far more potholes out there than crews realistically can fill until this summer, he said.

“At this point, you need to focus on the axle-breakers and leave the smaller ones behind,” Mr. Franklin said.

Ripe pothole climate

The science behind potholes is not as sophisticated as you might think.

Rain or snow falls on the pavement and seeps through its cracks. The water has to go somewhere. If the ground’s not frozen and water can penetrate the road’s base surface, the moisture can get absorbed in soil.

But the ground is now frozen — really frozen.

According to Don Moline, commissioner of customer service for the city’s utilities operations, the depth of frozen ground varies.

City officials have detected a frost line of 4 feet or more in some areas.

It is especially deep along the Anthony Wayne Trail, which could explain why the roadway is forming so many potholes.

City crews are noticing frozen ground several feet deep now in areas where digging is required to reach water mains or do other underground utility work, he said.

Water that collects below the road surface often freezes at night and expands, causing asphalt to pop, buckle, or warp.

The pothole-formation cycle is complete when passing automobiles roll over the softened pavement, kicking out chunks of asphalt.

Short-term solutions

Theresa Pollick, Ohio Department of Transportation spokesman, said potholes are typically repaired by a cold patch mix or by hot asphalt.

The hot asphalt mix is preferred because it’s more durable. But plants that produce that material often don’t operate during winter months.

One went into service recently, though, to provide hot asphalt to the city. State transportation department crews also used hot asphalt to make extensive repairs to I-75 near Detroit Avenue and on I-75 near I-475 in Perrysburg.

“The more freeze-thaw cycles you go through, the more chance there is of patch failure,” Ms. Pollick said. “In other words, if it freezes and stays frozen, it is much better than the temperature going up and down frequently, as we have seen in recent weeks.”

Officials put a lot of blame for this year’s potholes squarely on the shoulders of the polar vortex, that Arctic mass in the upper atmosphere that brings Arcticlike temperatures when all or parts of it stray away from the North Pole and migrate south.

Toledo and other Great Lakes cities had their first experience with that in 20 years in January, with temperatures dropping repeatedly below zero, breaking longtime nightly low temperature records.

That established a hard freeze in the ground, Mr. Welch and Mr. Franklin said.

But the question now is how much road salt and chemicals designed to melt ice from the roads adds to the problem of thawing during daytime and freezing at night, they said.

What does that mean for the future, especially if climate change results in a more frequent pattern of freeze-thaws?

“You start looking at cities in other climates and how they deal with it,” Mr. Welch said. “It might mean less salt and more sand.”

He said Toledo is experimenting with new road construction materials and pothole-patch mixtures, grinding up some chunks of broken pavement to see how they hold.

Search for answers

The federal government does extensive research into how roads, water lines, sewer lines, and other infrastructure hold up in cold regions at the U.S. Army Cold Regions Research and Engineering Laboratory in Hanover, N.H.

Several decades of scientific studies about potholes can be accessed via a Corps online database called the Engineer Research and Development Center Library, which can be found at http://​acwc.sdp.sirsi.net/​client/​default/? Type “potholes” into the search field.

Bryan Armbrust, a spokesman for the Army Corps of Engineers, which runs that laboratory, said Toledo usually doesn’t factor into the New Hampshire laboratory’s research because Toledo is not considered a cold region.

That may come as a surprise to area residents, some of whom may have read recently how Toledo’s average winter temperatures put it in the No. 11 spot for cold among cities with populations of 100,000 people or more.

This winter is one that Toledo-area officials plan to study for months, much like the Blizzard of ’78 — an event that resulted in a city manual for snow removal.

“When you have adversity, that’s when you take the time to grow,” Mr. Franklin said.

The challenge is trying to figure out what conclusions, if any, can be drawn from one of the coldest and now the snowiest winter in memory coming on the heels of three warmer-than-usual winters.

“I have never seen the severity of them like this before. I’ve seen big potholes, but I’ve never seen this many and this severe,” Mr. Welch said. “This obviously is very unusual for us.”

Mr. Franklin said it has given him reason to believe there is something about the Earth’s climate that is not right.

Toledo is likely one of dozens of cities in Pothole Alley that will be rethinking its strategies for maintaining road safety in the coming years, whether it be changes in how they apply salt or something else.

According to the federal Government Accountability Office, the nation’s roads, bridges, wastewater systems, and other forms of infrastructure “are vulnerable to changes in the climate.”

“When the climate changes, infrastructure — typically designed to operate within past climate conditions — may not operate as well or for as long as planned, leading to economic, environmental, and social impacts,” the GAO said, citing National Research Council studies.